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The present invention relates to connectors and more specifically to an interconnect system that utilizes conductive elastomeric columnar contacts to achieve conductive interconnection between opposing arrays of conductive contact pads.
Interconnect devices using elastomeric conductive members are known. One such interconnect device is disclosed in U.S. Pat. No. 6,056,557. In this interconnect device, conductive resilient members are disposed in holes in a substrate on a predetermined grid array and the assembly is positioned between adjacent printed circuit boards so as to make conductive contact between conductive pads on opposing boards.
Other connectors employing conductive elastomeric columns are disclosed in U.S. Pat. Nos. 5,599,193, 5,624,268, 6,271,482 and 6,348,659.
In board to device interconnect applications, such as board to Land Grid Array (LGA) or Ball Grid Array (BGA) devices it is important to maintain accurate positioning of the respective columnar contacts while avoiding distortion of the conductive elements that can result from the application of axial compressive forces to the contacts of the connector.
Accordingly, it would be desirable to have a connector system that employs conductive elastomeric columnar contacts that permit board to board or board to device interconnections and that maintain accurate alignment of the contacts in a predetermined array pattern. It would further be desirable for the contact positioning and shape to be resistant to distortion due to applied compressive forces that might adversely affect either the conductivity or positional accuracy of the contacts.
A connector for use in interconnect applications comprises a plurality of conductive elastomeric columnar contacts retained in an insulating substrate and arranged in a predetermined pattern. The elastomeric columnar contacts are each surrounded by a support column molded of an insulative polymer, such as silicone. In one embodiment, the support columns have a generally cylindral outer surface. The support columns provide mechanical support for and tend to reduce the deformation of the conductive elastomeric columnar contacts when the columnar contacts are subjected to compressive axial forces. Additionally, intermediate columns are formed between at least some of the support columns. The intermediate columns serve as mechanical stops and resist further compression of the connector in response to the application of excessive axial compressive forces to the contacts and the support columns. The location of the intermediate columns corresponds to the location of injection ports used in the molding of the intermediate columns and the support columns. Passageways are provided in the mold that allow for the flow of material from the point of injection at the respective intermediate column to one or more adjacent support columns. Insulative bridges are thus formed between the intermediate columns and the support columns in the location of such passageways. The height of the bridges above the substrate is equal to or less than the height of the intermediate columns above the substrate.
In one embodiment of the invention, a plurality of conductive elastomeric columnar contacts are supported by and retained in a substrate, such as a polyimide sheet, to form a contact assembly. The contact assembly is positioned in a mold and an insulative polymer, such as silicon, is injected into the mold to form the support columns and the intermediate columns. The columnar contacts have opposing tips that protrude slightly beyond the respective opposing end surfaces of the support columns to allow the tips of the columnar contacts to make conductive contact with corresponding pads located on printed circuit boards, an LGA device or a BGA device, as applicable. The height of the end surfaces of the intermediate columns is specified to serve as a mechanical stop so as to resist further compression of the connector in response to the application of excessive axial compressive forces on the contacts and the support columns.
A connector in accordance with the present invention may be produced by molding the conductive elastomeric columnar contacts in a first molding operation and by molding the support columns, the intermediate columns and the insulative bridges as an integral structure in a second molding operation.
In another embodiment of the invention an insulative substrate such as a polyimide sheet is provided having first and second pluralities of openings arranged in first and second hole patterns. Conductive elastomeric contact members are provided that extend through the first plurality of openings to form a contact member array, and insulative polymer columns or stops are provided that extend through the second plurality of openings. The contact members extend from the substrate a greater distance than the stops. The stops serve to limit the compression on the conductive elastomeric contact members when the connector is disposed between opposed contacting surfaces. In this manner, overstress on the conductive elastomeric contact members is avoided. The stops are located in non-abutting relation with respect to the contact members and may be selectively positioned within the array of contact members or on the periphery of the contact member array. The contact members and stops include a generally circumferential recess defining opposing shoulders, and the substrate is captured between the opposing shoulders of the recesses in the contact members and the stops to retain the contact members and the stops in position within the substrate.
The contact members and stops may be formed in first and second molding operations as discussed above.
Other features, aspects and advantages of the above described connector and methods of making the same will be apparent to those of ordinary skill in the art from the detailed description of the invention that follows.